1. Field of the Invention
The present invention relates to an image processing apparatus, in particular to an image processing apparatus capable of reproducing/displaying compressed image data.
2. Description of the Related Art
Proposals concerning an image processing apparatus capable of pipelining of multiple image processing include Jpn. Pat. Appln. KOKAI Publication No. 2000-311241, wherein low-capacity memories are connected in series between an image processing unit which performs JPEG processing (JPEG compression and JPEG expansion) and a scaling processing unit which performs scaling of an image (resize processing), thereby enabling the pipelining of the processing in these units. In Jpn. Pat. Appln. KOKAI Publication No. 2000-311241, image data processed in the image processing unit is stored once in the memory, and the stored image data is read in predetermined block units and then subjected to scaling processing.
A technique in Jpn. Pat. Appln. KOKAI Publication No. 2000-311241 will be described referring to FIG. 14. In an image processing apparatus of FIG. 14, a JPEG processing unit 102, a resize processing unit 103, a memory card 105 via a media interface 104, a memory (SDRAM) 106 and a video interface 107 are connected to a bus 101. Here, the JPEG processing unit 102 comprises an input DMA 102a, a JPEG compression/expansion section 102b, a buffer memory 102c and an output DMA 102d, while the resize processing unit 103 comprises an input DMA 103a, a resize section 103b and an output DMA 103c. 
In such a configuration, when the image stored in the memory card 105 is reproduced, compressed image data is first read from the memory card 105 via the media interface 104, and the read compressed image data is stored once in the SDRAM 106. Then, the compressed image data stored in the SDRAM 106 is read via the input DMA 102a in the JPEG processing unit 102. The read compressed image data is input to the JPEG compression/expansion section 102b where it is expanded. Expanded image data which has been obtained by the expansion in the JPEG compression/expansion section 102b is output to the bus 101 via the buffer memory 102c and the output DMA 102d, and stored in the SDRAM 106.
Subsequently, the expanded image data stored in the SDRAM 106 is read via the input DMA 103a in the resize processing unit 103. The read expanded image data is input to the resize section 103b where it is resized into a proper display size. Resized expanded image data is output to the bus 101 via the output DMA 103c, and stored in the SDRAM 106.
Then, the expanded image data stored in the SDRAM 106 is read by the video interface 107, thereby displaying an image on an unshown image display device such as a TFT-LCD.
Of the above processing, the expansion processing and the resize processing are performed sequentially in time as shown in FIG. 15. In the technique of Jpn. Pat. Appln. KOKAI Publication No. 2000-311241, if a user performs a key operation to reproduce an image, reading of the compressed image data is started via the media interface 104, and when the reading of the compressed image data is terminated, the expansion processing is started. When expansion of the compressed image data for one frame is terminated in the expansion processing, the resize processing is started, and the expanded image data is resized every predetermined block.